Do you often feel alone, even when surrounded by others? This feeling is no longer considered just a “blues”. Loneliness is now being studied as a real public health issue, with possible effects on mental health, the brain and the cardiovascular system.
The World Health Organization (WHO) estimates that around one in six people worldwide feel alone, or almost 16% of the population. Adolescents and young adults would be particularly affected.
Be careful, however, not to confuse loneliness with social isolation. Isolation corresponds to an objective lack of relationships or social contacts, while loneliness refers to the subjective feeling of not having the relationships that one needs or wants. We can therefore be very surrounded and still feel deeply alone.
And recent research shows that this feeling is worth taking seriously.
Can loneliness really change our personality?
This is one of the most surprising tracks.
A study published in 2024 in Personality and Individual Differences used data from 9,671 participants in the Health and Retirement Study, followed in 2012, 2016 and 2020. The researchers observed that loneliness was associated, over time, with a decrease in three personality traits: extroversion, agreeableness and conscientiousness. Conversely, higher levels of neuroticism were associated with more loneliness afterward.
This does not mean that loneliness automatically “changes” one’s personality. But the results suggest a relationship that can work both ways: Feeling lonely could promote certain changes in the way you interact with others, while certain personality traits can also make you more vulnerable to loneliness.
When emotions become more unstable
Loneliness doesn’t just seem to influence our relationships with others. It could also change the way we experience our emotions on a daily basis.
A study published in 2026 in Cognition and Emotion followed 252 adults aged 25 to 65 for 14 days, using repeated smartphone assessments. The loneliest participants showed greater emotional instability, particularly in their positive emotions. In other words, their emotional states varied more throughout the day.
Here again, it is impossible to say that loneliness is the direct cause of this instability. But these results suggest that the feeling of disconnection could be accompanied by a more fluctuating emotional experience.
In the brain, a “signature” of solitude?
Researchers are also trying to understand what happens in the brain when the feeling of loneliness sets in.
Work carried out using brain imaging data from the UK Biobank has notably found differences in several brain regions in people reporting feeling alone. A study published in Natural Human Behavior also analyzed 42,062 participants and 2,920 plasma proteins. She identified biological profiles associated with loneliness and social isolation, particularly in mechanisms linked to inflammation, antiviral responses and the complement system.
Even more surprising: more than half of the proteins associated with social isolation or loneliness were also linked, at follow-up, to cardiovascular disease, type 2 diabetes, stroke or mortality.
But be careful with interpretation: finding an association between loneliness and certain biological markers does not mean that loneliness directly causes these diseases. Other factors may intervene, and the researchers themselves underline the complexity of these mechanisms.
Can social networks reinforce the phenomenon?
Scrolling for hours sometimes feels like you’re connected. But this does not necessarily mean that the feeling of loneliness diminishes.
A longitudinal study published in 2026 in Personality and Social Psychology Bulletin followed Dutch adults for nine years. She found an association between passive use of social media and an increase in loneliness over time. More surprisingly, active use of social media was also associated with more loneliness.
These results do not allow us to conclude that social networks “make you lonely”. It’s also possible that people who already feel lonely use social media more. But they invite us to think about the quality of interactions rather than just the number of contacts.
And for the heart? The signal is taken very seriously
This is probably the best documented aspect.
The American Heart Association has published an extensive review of work on social isolation and loneliness. It concludes that there is an association with poorer cardiovascular health, including an increased risk of coronary heart disease and stroke. In this analysis, social isolation and loneliness were associated with approximately 29% increased risk of heart attack or death from heart disease and 32% increased risk of stroke.
The authors remain cautious, however: the estimates are relatively modest and certain confounding factors may explain part of the observed associations.
This does not prevent cardiologists from today considering social connections as an important element of overall health, in the same way as other factors linked to lifestyle.
Why we need to take loneliness seriously from a young age
The WHO emphasizes that loneliness does not only affect older people. Adolescents and young adults are among the groups reporting the highest levels of loneliness, with around 21% of young people affected according to the organization’s global estimates.
This development is particularly worrying because loneliness can be long-term and accompanied by other psychological difficulties.
However, feeling alone at some point in your life obviously does not mean that you will develop an illness. Loneliness is a state that can evolve, particularly when social conditions change and new connections are created.
Loneliness: the take-home message is not “see more people”
This is probably the most important point.
Being alone is not necessarily a problem. Feeling alone is when this feeling becomes lasting, painful and overwhelming.
The objective is therefore not necessarily to increase the number of outings or to fill your schedule. For some people, a deep, secure relationship can be more valuable than dozens of superficial contacts.
The WHO now considers loneliness and social isolation as a global public health issue and calls in particular for the development of interventions to strengthen social bonds.
If the feeling of loneliness becomes persistent, is accompanied by great sadness, anxiety, significant withdrawal or loss of interest in usual activities, talking to a health professional can be a first step.
Because contrary to popular belief, loneliness is not only a question of character. It is also a signal: that our needs for connection, support and belonging may no longer be sufficiently nourished.